Extracellular polymeric substances trigger an increase in redox mediators for enhanced sludge methanogenesis

Area of Science:

• Environmental Science
• Biotechnology
• Biochemistry

Background:

• Artificial redox mediators improve sludge methanogenesis but are costly and non-biodegradable.
• Developing cost-effective and environmentally friendly alternatives is crucial for large-scale applications.

Purpose of the Study:

• To investigate the potential of extracellular polymeric substances (EPS) as natural redox mediators for enhancing sludge methanogenesis.
• To evaluate the impact of EPS on methane production yield, lag phase duration, and sludge dewaterability.

Main Methods:

• Sludge methanogenesis experiments with and without EPS addition.
• Spectroelectrochemical measurements to analyze redox-active groups and charge transfer resistance.
• Analysis of protease activities, acetate concentration, and abundance of methyl coenzyme M reductase (mcrA) genes.

Main Results:

• EPS addition increased methane production yield by 83.5% and shortened the lag phase by 45.6%.
• EPS enhanced sludge dewaterability and decreased charge transfer resistance, improving extracellular electron transfer efficiency.
• EPS increased protease activities and acetate concentration, boosting acetotrophic and hydrogenotrophic methanogen activity.

Conclusions:

• Extracellular polymeric substances (EPS) are effective natural redox mediators for improving sludge anaerobic digestion.
• EPS offer a sustainable and economical alternative to artificial redox mediators, enhancing methane production and sludge quality.